1. The Field of the Invention
The present invention relates to a satellite signal receiver, and in particular, to a power controller for a satellite signal receiver used for devices, such as mobile terminals or mobile phones, that have a satellite signal reception unit.
2. Related Art
One conventional satellite signal receiver is known by Japanese Patent Laid-open Publication No. 8-304526, of which configuration is illustrated by FIG. 1.
The satellite signal receiver shown in FIG. 1 includes a positional information generator 1, operational command receiver 2, power supply 3, and power switching unit 4 that turns on or off power of the positional information generator 1.
The positional information generator 1 is equipped with an receiving antenna 5 for receiving electric waves that has been transmitted from satellites, satellite receiver 6, positional data output circuit 7, and transmitting antenna 8. The satellite receiver 6 demodulates a signal of the received electric waves to computes a current position of this apparatus. The operational command receiver 2 includes a receiving antenna 9 for receiving in wireless an operational command that has been received from the manager, and a reception circuit 10 via the receiving antenna 9.
When the receiver is in operation, only the power of the operational command receiver 2 is turned on to wait for receiving an operational command from the manager. When the manager transmits an operational command, the operational command receiver 2 receives the operational command and activates the power switching unit 4 so that it turns on. This unit 4 operates to supply the power from a power supply 3 to each element of the positional information generator 1, so that each element is energized. The satellite receiver 6 demodulates each satellite signal supplied from the antenna 5 in such a manner that a current position of this receiver is computed based on the signals from a plurality of satellites. The computed positional data are the subject to demodulation in the positional data output circuit 7, before being sent to the manager via the transmission antenna 8.
After the positional information generator 1 generates positional data, the power switching unit 4 will be kept to be on for a certain time, intermittently, or until receiving a command for stopping the operation. During the period of the on-state of the power switching unit 4, the generator 4 generates positional data.
According to this satellite signal receiver, if there is no need for demands for positional information, powering a main part of the apparatus is stopped, while the power is prepared whenever it is necessary. Hence consumption of useless power is suppressed.
However, the foregoing satellite signal receiver is configured so that an external command controls the turn on/off of power of the satellite receiver 6. Therefore, even when this receiving apparatus is located such that it is impossible for this apparatus to receive satellite electric waves or it is extremely difficult for this apparatus to perform such reception, thereby positioning being impossible, the external command causes the satellite receiver to be activated. This results in that the power is consumed uselessly.
An object of the present invention is to provide, with due consideration to the drawback of such a conventional satellite signal receiver, a power supply controller for a satellite signal receiver, which is able to control operational conditions of a satellite receiver depending on positioning conditions.
In order to accomplish the above object, the present invention provides satellite signal receiver comprising: a satellite signal reception unit for calculating a current position of the satellite signal receiver using an electric wave from a satellite, in response to a positioning request; a timer for clocking an elapsed time in calculating the current position of the satellite signal receiver; and power-on/off controlling means for controlling an on/off state of power supplied to both the satellite signal reception unit and the timer on the basis of information including the positioning request, the elapsed time clocked by the timer, and a condition under which the satellite signal reception unit receives the signal from the satellite.
Preferably, the power-on/off controlling means includes: switch means for switching on or off the power supplied to both the satellite signal reception unit and the timer; and control means for controlling turn on/off operations of the switch means based on the information. It is also preferred that the information about the condition is information about the number of ephemerides. In this case, preferably, the control means includes first control means for turning on the switch means in response to the positioning request, setting means for adjustably setting a period of active time counted from a first time instant at which the switch means turns on to a second time instant at which the satellite signal reception unit calculates the current position, and second control means for turning off the switch means when the elapsed time reaches the period of active time. Byway of example, the setting means is configured so that larger the less the number of ephemerides, the larger the period of active time.
Still preferably, the information about the condition is information about an elapsed time from the last calculation of the current position.
As a further configuration according to the present invention, there is provided a satellite signal receiver comprising: a satellite signal reception unit for intermittently calculating a current position of the satellite signal receiver at adjustable intermittent intervals by using an electric wave from a satellite; a timer for clocking an elapsed time every time when the current position of the satellite signal receiver is calculated; and power-on/off controlling means for intermittently controlling an on/off state of power supplied to the satellite signal reception unit on the basis of information including the elapsed time clocked by the timer every time when the current position of the satellite signal receiver is calculated.
According to the above constructions, the power supplied to both the satellite signal reception unit and the timer, or to the satellite signal reception unit is turned on in response to a positioning request issued or at intermittent intervals. During such supply of the power, the power can be turned on/off to control a period of time for supplying the power or intermittent intervals for supplying the power, according to information held by the satellite signal reception unit or its receiving condition. Thus, in cases the satellite signal receiver is placed at situations in which the positioning is impossible, the time for supplying of the power is shortened to avoid useless consumption of the power.